Tony Hayward at BP and Jeroen van der Veer at Royal Dutch Shell have a great deal in common.

Both took over as chief executives when their companies were in crisis: van der Veer after the Shell reserves misreporting scandal that emerged in 2004 and Hayward after the fatal explosion at BP's Texas City refinery in 2005 and other problems drew attention to deep operational weaknesses.

Both face the same challenge of how big international oil companies, confronted by ever more assertive governments and national oil companies, can get access to the resources they need to survive.

In this difficult terrain, they are on divergent paths.

Their differences can be traced in part to the companies' origins. Shell Transport and Trading, the British parent of today's Shell, was originally a shipping company, the pioneer of oil tankers. Its alliance with Royal Dutch built a strong marketing business before World War I.

BP's roots lie in oil exploration, with a big find 100 years ago in what is now Iran.

That differing corporate DNA has shaped the companies' fortunes ever since.

It is not that BP cannot do refining: its refineries outside the US perform as well as anyone's. But its US refineries have been a persistent problem: not just in the Texas City tragedy in 2005, but in the slow pace at which the refinery has been brought back on stream following Hurricane Katrina later that year, and in the fire at Whiting in Indiana in March, which has kept it working below full capacity.

Those troubles meant that much of BP's capacity was unavailable during one of the best periods on record for US refiners. The US refineries lost more than $800 million last year.

Profits

Worldwide, BP made a $2.62 billion profit from its refining and marketing segment; a performance described by Hayward as "very disappointing". Shell, by contrast, made $6.95 billion from its refining and marketing business.

Upstream, on the other hand, BP seems to have the edge. It is not that Shell is incapable of conventional exploration. It said last week it had found about one billion barrels of oil equivalent (boe) to add to its resource base last year, although that figure is different from the definition of proved reserves accepted by the US Securities and Exchange Commission.

However, Shell has not yet given any guidance on what its reserve replacement will have been according to those SEC rules. The number, due out in a few weeks, is likely to look bad. There will be a hit of 1.1 billion boe from the gross reserves figure as a result of selling half of Shell's stake in the $20 billion Sakhalin 2 project to Gazprom, even though the net loss is only 400 million boe.

There is a similar contrast in the two companies' near-term production outlook. BP has new projects such as ACG3 in Azerbaijan, Thunder Horse in the US and Tangguh in Indonesia coming on stream this year. If oil prices average about the same as last year, BP could expect one or two per cent growth in production, while Shell would expect a fall, for a sixth successive year.

Looking into the next decade, though, Shell expects to come into its own, thanks to big investments in "unconventional" sources. Its capital spending this year at $28 billion to $29 billion is more than 30 per cent higher than BP's plans. That spending is going into projects such as the oil sands of Alberta and liquefied natural gas at Sakhalin 2.

As Neil McMahon of Sanford Bernstein puts it, comparing the companies to wines: "BP will drink well over the next few years, whereas Shell will be better after 2010."